lathrop



Oct. 10, 1950 H. F. LATHROP 2,524,813

comm. FOR REFRIGERATION SYSTEIIS Original Filed April 26, 1944 Inventor: Haw-"dd E Lathrop, by 1- ,His Attorney.

2,524,813 oon'rnor. F'Qlit @EWEGEFZKATKQN SYETEiMfi {Ens-old F. Letllirop, Ihliadelphin, Fan,

resigns: to

general Electric @ornpnny, a corporation of New 'iicrh Griginal application April cs, 19%, Eerie] No. pissed and this application October 21, 1947, Serial No. 713L143 2 Claims.

This inventioi. relates to refrigerating systems and particularly to such systems which are operated at very low temperatures. This application is a division of my copending application Serial No. 532,773, flied April 26, 1944.

In the conventional thermostatic expansion valve there is provided an actuating member responsive to the pressure within the evaporator and which is opposed by an actuating member responsive to the temperature of the refrigerant in the suction line. The pressure responsive member tends to open the valve upon a reduction in pressure and, consequently, when the refrigerating machine is started after an idle period the valve will be opened as soon as the operation of the compressor has reduced the pressure suii'icicntly to actuate the pressure responsive memher. I my copending application Serial No. 582,772, flied April 26, 19M, and which has now matured into Patent No. 2,497,677, granted February 14, 1950, and assigned to the some assignee as the present invention. there is described and claimed a thermostatic expansion valve actuated in response to the difference between the suction line tcmp'rature and saturr'lon temperature in the evaporator of the refrigerating system.

When a thermostatic expansion valve is constructed as described in the above mentioned copending application Serial No. 532,772, the member responsive to the saturation temperature of the liquid re rigerant tends to close the valve upon a rise ir. temperature, and should there be no liquid refrigerant in the evaporator when the machine is started, there would be no reduction in temperature sufllcient to cool the feeler bulb of the saturation temperature responsive member and open the valve. In my last mentioned copending application an arrangement is described for insuring the presence of liquid refrigerant in the vicinity of the saturation temperature responsive control bulb and thereby insuring the opening of the valve when the operation 0! the system is started. It is an object of my present invention to provide a refrigerating system having an expansion valve controlled by the temperature of the suction gas and the saturation temperature of the liquid refrigerant in the evaporator and provided with an improved arrangement for assuring opening of the valve and up eration of the system even though the liquid refrigerant in the evaporator houid have been removed prior to starting.

which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of this invention reference may be had to the accompanying drawing the single figure of which illustrates diagrammatically a compression type refrigerating sy tem provided with a control embodying my invention.

Referring now to'the drawing, the refrigerating system illustrated includes a compressor l driven by an electric motor (not shown) and arranged to supply hot compressed refrigerant to a condenser 2. The condenser 2 is cooled by water circulated through a receiver or jacket 3 and the compressed refrigerant is liquefied and flows to a liquid receiver 4. The liquid refrigerant from. the receiver 4 is supplied to a multiple conduit evaporator ll through a liquid line 8 by operation of a solenoid actuated expansion valve 1. The evaporator 5 comprises a plurality of parallel conduits connected to an outlet connection 8 of the valve 1 by a refrigerant distributor 8 which divides the refrigerant equally among the several conduits. The refrigerant in the evaporator ab- Further objects and advantages of my inven- I tion will become apparent as the following desoription proceeds, and the features of novelty sorbs heat from the air to be cooled and is vaporized, and the vaporized refrigerant is returned to the compressor I through a suction line H manifolded to the several evaporator conduits. The solenoid valve 1 is actuated by a control l2 so that it operates to perform the function of a thermostatic expansion valve and maintain a. predetermined amount of superheat in the vaporized refrigerant withdrawn from the evaporator. For this purpose the control I! is provided with a temperature responsive device' It including an expsnsible chamber formed by a bellows It. The interior of the chamber is in communication through a tube It with a feeler bulb or temperature responsive element ll secured to the suction line 3| so that it is responsive to the temperature of the vaporized refrigerant withdrawn from the evaporator. The control I! is also provided with an expansible chamber device ll arranged in 0pposed relation to the device lland comprising a bellows i8 forming an expansible chamber which is in communication through a tube is with a temperature feeler bulb 20. The feeier bulb 20 is secured in heat exchange relation with a liquid collecting sump 2| secured in communication with the lowermost conduit of the evaporator indicated at 22. The sump 2 I, during the normal operation of the evaporator, contains liquid refrigerant, and the device ll is, therefore, actuated in accordance with the saturation temperature of the liquid refrigerant in the sump 2i.

Tho liquid rcirlgcrcnt in tho sump ll in ct tho pro-scum of tho rofrlgoront in tho evuporctor so that tho temporcturc of the sump is the octumtion temperature of tho liquid refrigerant in the evcporator. In some constructiona there may be a substantial prc'caure drop between the inlet and of the evaporator conduits and the auction lino H; and, in such cases, the sump 2| may be located nccror the outlet end 01 the evaporator conduit so that the pressure in the'sump in the come d: the suction line prcosure and the tempcrcure of the liquid refrigerant in the sump la the eoturction temperature of the refrigerant at the prcocure in the suction line.

This sysfom is particularly applicable to instcllntions in which a plurality of evuporators are supplied from a single refrigerant condonelng unit. The system is arranged to cool a storage chamber or other refrigerated area. enclosed by a. tbcrznelly insulated wall 23, the multiple conduit cvcporotor 5 being arranged within this chombcr. Upon d demand cooling in the enclosed by the wall 28, a thermostat 2d closes itn contccts and energizes the solenoid vnlvo I provided that a, switch in the solenoid lino boo been closed. The actuation of the switch 2 5 1.8 controlled in accordance with the suporheot in the suction line H by operation of the op posod cctuoting mcmbas II and ll. The switch 25 includes 2. switch arm 26 which is moved in cccorddnoe with changes in the difiercnce oi the pressures in the momboru I; and IT. The switch arm 2t:- lc pivoted ct its lower end to c stotioncxy pivot ill and the movement produced by the actumombers ii: and H is translated into pivotnl movement of he arm 26 through coupling mom u 26% and and c pontogrcph conetructc oi lions 51-3, 3%, 32 and 33. The links 39 and 33 are pivoted together on the coupling 28; and limi s Si and 32 are similarly pivoted on the coupling the lower ends of the limbs do and iii are pivoted at 37; and the upper ends of the links dnd 33 are pivc scd together and their pivot is clidnbly mount-ed in o slot M in the arm 28. The couplings E8 and 23 are held open-t and in engagement with actuating rods 35 and 8b of the dcviccs l3 and I1, respectively. by a suitable compr rsion spring 31. The movement of the photograph and resulting pivotal movemeat of the arm 26 are determined by the difference between the forces of the oppobod devices 13 and I1. The cwitch 2b includes front and boob: contccm 3d and 38, respectively. The arm 25 under norzncl operating conditions is biased by c superheot adjusting spring 50 to a position intcrmcdiute the contacts 3% and 3% so that the solenoid valve is not energized when the amount of suporheot is below a predetermined value. When the supcrhect rises. a contact 6! on the arm 25 engages the contact 33 and closes the circuit of the solenoid of the valve I thereby opening the valve and admitting more refrigerant to the evaporator and lowering the amount of supcrhect to the predetermined desired value.

Thus under normal conditions of operation the control devices [3 and I1 cooperate to maintain a value of supcrheat of the vaporized refrigerant in the suction line H determined by the setting of the spring by turning of an adjusting screw 42; and during normal operation increased pressure in the element i3 tends to open the valve while increased pressure in the element I1 tends to close the valve. It is apparent, therefore, that on an increase in temperature or the feeler bulb 29 the control device I! tends to close the valve, 11 or coy reason the temperature oi d tho bulb id is obnormclly high and there is no liquid mirigemnt in the bump 2| to cool the elemcni, 26. it would be impossible to open the valve automatically if some arrangement other than the controls as just described were not provided.

In order to insure opening of the valve upon starting the operation or the refrigerating system, the sump 21 is aupplied'with heat by an electric heater 4! which is energized on closing of the thermostat 24; the fceler bulb I6 and heater 3, together with the lower portion of the bump 2|, are enclosed in an insulated casing M. It will readily be apparent that should there be no liquid refrigerant in the sump II when the thcrmoctct 24 closes its contacts on a call for cooling, the feeler bulb 28 will be heated directly by tho hector 43 and the pressure in the device i'l will rise to o. high value. The arrangement of the switch arm 26 is such that when thin high value of premure prevails in the device II, the arm in rotctcd about the pivot 11 so that a. contact do engages the book contact 39 and energizes tho colonoid oi the valve 1 to open the valve thcroby admitting liquid relrigorant to the evaporator and placing the system in condition for normal operation to maintain the desired amount oi cupcrheat.

The cuperheat characteristics of the system mrsy further be improved by providing a preaeure compensating device 48 directly connected with the suction line through a. tube 41 and arranged to hm the switch arm 26 in a clockwise directlon no that the bellows 46 tends to keep the switch contccts 33 and GI out 0! engagement until u predetermined low pressure has been attnincd in the evaporator. The superheat setting is then determined by the suction line pressure, which is transmitted to the pressure respomlvo element 48 in addition to the setting of the adjustable spring 4e. This arrangement provides compensation of the auperheat setting with pressure changes and results in a more constunt value of suporheat over a wide range of operating tcmmratures. It has been found that a valve provided with this additional control my be mode to maintain superheat within a range of lens than 5' F. over a. range of evaporator temperatures from 0 F. to F.

During the operation of the refrigerating ayetern, liquid mfrigerant may be available at all timea in the liquid line 0 at the solenoid I; however, the evaporator is supplied with refrigerant only on demand determined by the thermostat 24 which is responsive to the temperature within the space to be cooled. Upon a demand for cooling, the operation of the valve 1 and its accoclatcd control mechanism is 'such that a predeterrnlncd value of superheat is maintained in the suction line H. Should all the liquid refrigerant in the evaporator have been vaporized during a period when there is no demand for cooling. then the excessive pressure created in the control device H by the heater 43 upon starting rotates the arm 2b to close contacts 39 and ii. This energizes the solenoid oi the valve 1 and insures admission of suillclent liquid refrigerant to the evaporator to enable the control to take up its 5 sure gitd such as ethane; however. in order to obtain other characteristics it may be desirable to charge one of the devices with one see and the other with a different gas or one or both of the devices with a vaporizable liquid.

While I have illustrated my invention in connection with'the compression type refrigerating systems, other applications will be apparent to those skilled in the art nhd I do not, therefore. desire m invention to be limited to the particular construction shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope 0! my invention.

What I claim as new end desire to secure by Letters Patent of the United States is:

1. In a refrigerating system including a con denser and an evaporator and means for withdrawing vaporized reirinerunt from Said evaporotor and returning it to said condenser. an expension valve for controlling the flow of refrigeront from said condenser to said even Jrator. a solenoid for actuating said valve, on electric circuit for sold solenoid, control means including a switch in said electric circuit for energizing said solenoid and for actuating said valve to mainthin a predetermined amount of superhest in the refrigersnt withdrawn from said evaporator, said control means including two opposed expunsible chamber devices for actuating said switch. one

of said devices being responsive to the temperature of the vaporized refrigerant withdrawn from said evnporetor and the other being responsive to the saturation temperature of the liquid reirigerent in said evaporator, both said devices tending to close said switch when the pressure in their respective chambers overcomes the prossure in the chamber of the opposed device, and biasing means for adjusting said devices to determine the amount of superheat maintained by said control means.

2. In a refrigerating system including a. condenser and an evaporator and means for withdrawing vaporized refrigerant from said evaporetor and returning it to said condenser, a solenoid operated valve for controlling the admission of liquid refrigerant to said evaporator, an electric circuit having a switch therein for energizing said solenoid, temperature responsive control means for actuating said switch. said control means comprising opposed temperature responsive expansible chamber devices arranged to close seid switch upon a predetermined change in the differential pressure between said devices. one or said devices having a feeler element arranged to be responsive to the saturation temperature of the liquid refrigerant in said evaporator, and means dependent upon the absence of liquid refrigerant in said evaporator for heating said ecler element to unbalance said control means and open said valve.

HAROLD F. LA'I'HROP.

REFERENCES CITED The following references are of record in the tile 01 this patent:

UNITED STATES PATENTS Number Name Date 2,165,519 Stolz July ll, 1939 2,280,425 Benders Apr. 21. 1942 2,383,010 Mattheson Nov. 21, 1944 2,379,286 Dodson June 26, 1945 

